On-site purification of problem petrolic liquid fuels

ABSTRACT

SOUR CRUDES AND RESIDUAL OILS, OFTEN HIGH IN DELTERIOUS ASH CONTENT AND OF A TYPE OBTAINED RELATIVELY INEXPENSIVELY FROM ABROAD, ARE USABLE FOR BURNING TO GENERATE HEAT, AS FOR STEAM GENERATION, WHILE COMPLYING WITH UPDATED AIR POLLUTION REGULATIONS UPON TREATING AND PURIFYING THE CURDE OR RESIDUAL OIL AT OR ADJACENT THE SITE OF THE BURNER SYSTEM AT A RATE SUBSTANTIALLY COINCIDENT WITH THE RATE OF CONSUMPTION BY THE BURNER SYSTE, USUALLY WITH A SURGE TANK IS SERIES TO SMOOTH OUT FLUCTUATIONS IN BURNER OPERATION OR TO ACCOMMODATE BRIEF SHUTDOWNS OF THE TREATMENT AND PURIFICATION EQUIPMENT. THE APPARATUS OF THE INVENTION CONSISTS OF THE COMBINATION, WITH A BURNER SYSTEM, OF A RESERVOIR FOR THE CRUDE OF RESIDUAL OIL, MEANS FOR CONVEYING SUCH PETROLIC LIQUID TO RESPECTIVE CONTACTORPURIFIERS FOR REMOVING EITHER SULFUR COMPOUNDS, OR ASH CONTENT, OR BOTH, AND, WITHOUT A SURGE TANK, MEANS FOR CONEYING THE PURIFIED OIL TO THE BURNER SYSTEM. IN A PREFERRED EMBODIMENT THE APPARATUS IS AUTOMATED IN A COMPLETELY INTEGRATED FORM.

May 23, 1972 v p, GARWOOD 3,664,802

ON-SITE PURIFICATION OF PROBLEM PETROLIC LIQUID FUELS Filed March 11, 1971 SIGNAL FROM PROCESS CONTROL POM/T 41 BURNER AIR- SUPPLY C OMPU 7? R RAT/O C ON MAKE; up

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United States Patent Ofiice 3,664,802 Patented May 23, 1972 3,664,802 ON-SITE PURIFICATION OF PROBLEM PETROLIC LIQUID FUELS Eric P. Garwood, 128 Naperville Road, Clarendon Hills, Ill. 60514 Filed Mar. 11, 1971, Ser. No. 123,146 Int. Cl. F23k 5/00 US. Cl. 431-3 17 Claims ABSTRACT OF THE DISCLOSURE Sour crudes and residual oils, often high in deleterious ash content and of a type obtained relatively inexpensively from abroad, are usable for burning to generate heat, as for steam generation, while complying with updated air pollution regulations upon treating and purifying the crude or residual oil at or adjacent the site of the burner system at a rate substantially coincident with the rate of consumption by the burner system, usually with a surge tank in series to smooth out fluctuations in burner operation or to accommodate brief shutdowns of the treatment and purification equipment. The apparatus of the invention consists of the combination, with a burner system, of a reservoir for the crude or residual oil, means for conveying such petrolic liquid to respective contactorpurifiers for removing either sulfur compounds, or ash content, or both, and, with or without a surge tank, means for conveying the purified oil to the burner system. In a preferred embodiment the apparatus is automated in a completely integrated form.

BACKGROUND OF THE INVENTION (1) Field of the invention The invention relates to a process for removing either or both of sulfur compounds and deleterious ash content from problem oils such as sour crude or sour residual oil at the site adjacent where it is to be used and at a process rate substantially commensurate with the rate of consumption of the treated oil in one or several burner systems supplied thereby. The invention further relates to a combination of apparatus for carrying out such process.

(2) Description of the prior art I-Ieretofore coal and fuel oil have been the major source of fuel for large fuel consuming burners such as those used in power plants to generate steam for production of electricity or to supply heat 'for other requirements, or those used to generate power as components of turbine engines. However, in order to comply with recent air pollution control laws these plants generally are discovering that they require fuels with a lower sulfur content than they are now receiving from their conventional fuel sources. The amount of low sulfur coal is limted and low sulfur fuel oil generally is being sold at a substantial premium. Installation of equipment to remove the sulfur compounds from the stack gases is discouragingly expensive in existing plants and is still in the de velopment stage.

Due to the shortage of fuel which occurred in 1970, interest is being shown in using foreign crudes for fuel oil. Favored treatment to utility companies allow, or plans are under way to allow, duty-free import of these foreign oils direct to power plants. A major disadvantage of most foreign oils is their high sulfur and/or ash content, therefore it may be particularly necessary to reduce the sulfur and ash content prior to shipment to the United States as this oil must presently be shipped directly to the site of consumption and cannot be sent first to another site for treatment. Even if diversion shipment to a refinery for treatment were allowed at some future time, it would add greatly to the cost of the oil. Most foreign crudes must be shipped considerable distances from the area of their production to a refinery for de-sulfurization and de-ashing and such shipment and handling adds greatly to the cost of the oil.

Purification methods and means for treating oils are generally broadly known for either batch or continuous operations. Sulfur is removed by contacting the contaminated oil with a solvent for the sulfur compounds which is not miscible with the oil and thus is readily separated therefrom. Such a solvent is concentrated sulfuric acid containing H of, for example, about to 93 percent, or greater, concentration. The ash content of these oils, particularly the sodium and vanadium content, which as sodium oxide and vanadium oxide corrode and attack boiler parts and internal combustion turbine parts, all such parts being herein referred to as burner components, is reduced by contacting the oil with an aqueous solution of a suitable soluble inorganic compound such as a 20 to 30 percent by Weight aqueous solution of magnesium sulfate.

OBJECTS OF THE INVENTION It would be desirable and is an important object of this invention to provide a method whereby oils can be shipped from the locale of production directly to the site of fuel consumption and whereby the oil is de-sulfurized and/ or de-ashed prior to consumption at a rate sufiicient to satisfy the requirements of the site, thus avoiding the added expense of shipping the oil to a refinery before or after delivery to the site.

In particular it is an object of this invention to provide a process for de-sulfurizing and/or de-ashing fuel oils at a rate to satisfy, coordinately, the demands of a burner system or several systems operated concurrently.

It is a further object of the invention to provide a practical process for removing sulfur compounds, sodium compounds and vanadium compounds from sour crudes, sour residual oils, and sour fuel oils, particularly the inexpensive foreign oils, in a relatively low cost operation at the site where such oil is to be burned for the production of heat, e;g., in a high pressure boiler for electrical power generation, or for production of power as in an internal combustion turbine, while avoiding expensive shipping costs to a conventional refinery or treatment plant, while minimizing storage costs and regulations and while meeting the requirements of air pollution regulations.

A further object of the invention is to provide a physical system for carrying out the process of the invention, particularly in an integrated automated fashion.

STATEMENT OF THE INVENTION The invention is based on the discovery that upon conveying a sour crude or sour residual oil, with or without a high ash content, herein referred to as a problem petrolic liquid, from a reservoir, which is the only reservoir needed, to a contactor-purifier for the partial removal of either or both of sulfur compounds, or ash content, such as sodium compounds, and/or vanadium compounds, which contactor-purifier is operated at substantially the rate of consumption of an accompanying burner system, and conveying the purified oil to the burner system with or without passing it through a surge tank on its way to the burner system, substantial economies are effected in fuel costs as well as in operating costs of the burner system while readily maintaining the concentration of sulfur or sulfur compounds in the stack effluent from the burner system below the maximum permitted by air pollution requirements, while the ash content in the treated fuel is low 3 enough to minimize damage to equipment, such as for example, nozzle tips, boiler tubes, and the like burner components.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The process of the invention may be carried out on most any crude oil, residual oil or other fuel oil which presents a problem in its utilization in a heat or power generation system because of the presence in such oil of an objec tionable amount of sulfur or sulfur compounds, or a deleterious amount of ash, or both such types of contamination or problem impurity, and for the purposes of the following description and the appended claims such an oil is referred to as a problem petrolic liquid. A problem petrolic liquid containing a concentration of sulfur compounds, which, on combustion, will yield a stack effluent containing sulfur or sulfur compounds greater than that allowed by air pollution regulations is herein referred to as a sour crude or sour petrolic liquid. Currently sour crudes are so classified if they contain about 0.5% by weight or more sulfur or sulfur compounds (expressed as sulfur) but it is anticipated that such classification will in the future attach to oils containing as little as 0.2% by weight or less of sulfur or sulfur compounds. Residual oil is a term having the usual meaning, viz, the petroleum fraction remaining after removing from crude oil those compounds having about 12 carbon atoms or less. The term generation of heat is meant to include burning the petrolic liquid in burners heating a steam boiler as well as in burner within a turbine engine.

The problem petroilic liquid is transported or conveyed from storage, as in a tank adjacent the burner system, i.e., within about 1 or 2 miles of the burner system but most usually a tank not more than about one-quatrter mile away, as by pumping the oil through a pipe to a contactorpurifier in which sulfur compounds are partially removed from the oil, preferably below about 0.2% by weight, and more preferably below about 0.05% by weight or as required by air pollution regulations. Sulfur compound removal is carried out continuously or by batch processing by any of the ways known to the art in which a solvent for sulfur compounds which is immiscible with the oil is brought into contact with the oil in a co-current or counter-current manner or by mixing and separating batch-wise, or by continuously mixing and counter-currently separating centrifugally in a continuous centrifugal contactor of the type supplied by Chemical Machinery Division of Baker Perkins, Inc., and referred to as a Podbielniak separator. Such a separator as well as two other suitable types of centrifugal separators are fully depicted and described by D. 0. Todd and W. I. Podbielniak in Advances in Centrifugal Extraction, Chem. Eng. Prog. 61, No. 5, 6973 (May 1965). Other suitable solvent extraction processes and equipment are described by Carl Hanoon in Solvent Extraction appearing in Chem. Eng. 75, No. 18, 76-98, (Aug. 26, 1968).

Other contacting devices which may be used include, but are not limited to the following: sieve tray columns, gravity columns, mechanical agitated columns, Graesser raining bucket contactors, and pulsed columns. Due to the nature of the materials and compactness desired, centrifugal contacting devices are well suited for this process. Contacting systems can be operated batch-wise or continuous, the most efficient operation generally being continuous counter-current.

Suitable solvents include concentrated aqueous sulfuric acid containing about 85 to 94 percent by weight, or greater, H 50 including for example 20 percent oleum, and, molten, i.e., liquified, phenol, compressed and liquified sulfur dioxide, and sulfolane (thiocyclopentane-l,1- dioxide).

Processing of the oil for sulfur removal is essentially carried out at a rate substantially equal to the overall rate of consumption of the burner system so that there is little or no need for storage of treated oil, and is preferably carried out by keying the rate of the purifying operation flexibly to the rate of consumption by the burner system. For the purposes of the present description, however, processing at a rate equal to burner consumption also is meant to include operations in which purification is carried out batch-wise at an average rate suflicient to provide the needs of the burner system. To effect the smoothing out of the supply for the burner system a surge tank is provided and acts as part of the means for conveying the treated oil from the last contactor-purifier being utilized to the burner system. Such means for conveying the treated oil to the burner system necessarily includes a pump and the requisite piping between the contactor-purifier and the burners, or, from the contactor-purifier to a surge tank and from thence to the burners.

In general, it is highly desirable that the system include a contactor-purifier for the partial removal of the ash content of the problem petrolic liquid, especially the sodium compounds and vanadium compounds as aforementioned. Such purification is carried out concurrently, that is, either before or after the treatment for partial removal of sulfur compounds, but preferably after such treatment, and in series therewith, with all the treated oil being subjected to both purification processes in consecutive manner. However, the system should be set up to carry out either or both of two types of purification since some high ash content oils occur which are not sour oils.

Partial removal of sodium compounds and vanadium compounds is effected by contacting the oil with an aqueous solution of a water soluble inorganic compound capable of complexing or otherwise taking up and extracting vanadium, such as a 15 to 40 percent, and more preferably, 20 percent by weight aqueous solution of magnesium sulfate or other readily soluble magnesium salt. Contacting is carried out readily in any of the types of apparatus described above for the removal of sulfur compounds, but preferably in the centrifugal type contactor. The sodium compound content should be lowered below 5 p.p.m. and, more preferably, below about 3 p.p.m., expressed as Na. The vanadium compound content should be lowered below about 60 p.p.m. and more preferably, below about 40 p.p.m. expressed as V. The reactions of magnesium with vanadium compounds in oils is the subject of a study reported by W. D. Nills and H. R. Sanders in Paper No. 60-WA-278, printed and reported to the Winter Annual Meeting, New York, N.Y., Nov. 27-Dec. 2, 1960 of the American Society of Mechanical Engineers.

Following the latter of the purification steps employed, the oil is conveyed as described by a pump and piping to the burners, generally after passing the oil through a surge tank after the last or each purification step. It is considered to be within the scope of the invention to convey the treated oil by any convenient means to a burner system or systems not more than about twenty miles away, but generally not more than about 1 or 2 miles away.

The treated oil must be sutficiently low in sulfur compounds to produce a relatively low concentration of sulfur and sulfur compounds in the stack efiluent of the burner system, generally not over 20 p.p.m., and preferably below about 10 p.p.m., expressed as H 50 or such lower figure as may be set by air pollution control authorities.

Referring now to FIG. 1 of the drawing there is seen a schematic representation of an arrangement of parts used according to a preferred embodiment of the invention. Problem petrolic liquid such as sour crude oil or residual oil, for example, from a large ocean-going tanker, is transferred to a tank or reservoir 10 from whence the petrolic liquid is drawn for treatment concurrent with use. Petrolic liquid from the reservoir 10 is moved by the pump 11, which may be a gear pump or other positive displacement pump through a filtration unit 12 to booster pump 13. The booster pump 13 sends the oil through a flow meter 14, and thence along one of the alternate paths according to processing requirements, as directed by the valves 15 and 16.

With valve 15 open and valve 16 closed, the petrolic liquid is directed through a first heat exchange unit 17 in which the temperature of the liquid is adjusted up or down as required for operations in the treatment immediately following.

An oil-immiscible solvent for extraction of sulfur compounds is brought into the line containing the thermally regulated petrolic liquid and the combined stream is fed into a first contactor-purifier 18. The oil immiscible solvent, typically concentrated sulfuric acid, is supplied to the said combined stream by pump 19 drawing the solvent from reservoir 20 and conveying it to the combined stream through a line controlled by throttle valve 21. The contactor-purifier is a device in which immiscible liquids are mixed and separated as by any of mixer-settler, or counter-current, or co-current principles of liquid-liquid extraction and operated batch-wise or continuously but preferably, is a continuous centrifugal contactor, particularly the Podbielniak extractor. Immiscible solvent containing sulfur compounds is discharged partly through throttle valve 22 to waste, but more preferably is discharged partly to means (not indicated in detail) for the recovery of the immiscible solvent freed from the sulfur compounds and re-use in the present process. Recovered solvent becomes part of the make-up solvent to keep an adequate supply in reservoir 20.

The petrolic liquid with reduced content of sulfur compounds is discharged from the contactor-purifier to one of two alternate paths according to process requirements, as directed by valves 24 and 25. With valve 24 open and valve 25 closed, the petrolic liquid is directed through a second heat exchange unit 26 in which the temperature of the liquid is adjusted up or down and required for operations in the treatment immediately following.

An aqueous solution of an inorganic compound capable of extracting with or without reacting therewith vanadium compounds, and capable of extracting sodium compounds, is brought into the line containing the thermally-regulated petrolic liquid and the combined stream is fed into a second contactor-purifier 27. The inorganic compound solution, typically a magnesium sulfate solution, is supplied to the same combined streams by pump 28, drawing the aqueous solution from the reservoir 29 and conveying it to the combined stream through a line controlled by the throttle valve 30.

Within the contactor-purifier 27 the combined liquids are mixed and separated according to liquid-liquid extraction principles, but preferably, by the continuous centrifugal contactor method, and used aqueous inorganic solution is discharged partly back to the reservoir 29, and partly through throttle valve 31 to waste or to means (not shown in detail) for the recovery of the inorganic solution freed from sodium compounds and vanadium compounds. The throttle valves 30 and 31 are controlled by the ratio controller 23, each ratio controller receiving guiding signal from the flow meter 14.

The petrolic liquid with reduced ash content, with respect to sodium compounds and vanadium compounds is discharged from the second contactor-purifier 27 through valve 33 and either through valve 34 directly to throttle valve 35, or, On closing valve 34, to a surge tank 36 from which the liquid is drawn by pump 37 and directed through valve 38 to the same throttle valve.

Treated, i.e., purified petrolic liquid, is fed to the burner 39, along with an air supply controlled by an air control unit 40. Meantime, a sensor 41 located in or about the boiler or gas turbine engine, or whatever incorporates the burner per se detects a pre-selected phenomenon such as steam pressure or temperature or shaft speed, each of which are related to burner consumption of the feul, i.e., the petrolic liquid, and generates a signal from the sensor in proportion thereto. Maintenance of coordinated operations is highly essential to the success of an economically successful unit and thus it is generally necessary and indeed quite advantageous to subject the whole thing to automatic control. Accordingly the signal from the sensor is directed to a computer 42 which is pre-programmed to control the air supply through air control unit 40 and the fuel supply through throttle valve 35 to obtain proper fuel combustion and at a desired rate. An example of such a computer is the Model 571 Syncro Optimizer manufactured by Moore Instrument Company.

In the foregoing manner a pre-selected level of thermal or power output is maintained and the rate of fuel processing is maintained accordingly so that no storage is required for treated fuel apart from the smoothing out effect of using a surge tank, which is usually desirable.

If desired, using the present apparatus, the first contactor-purifier 18 and associated reservoir and other parts may be set up to handle the removal of sodium compounds and vandium compounds where the second contactor-purifier 27 may be set up to handle the removal of sulfur compounds, as the order in which the purification procedures are carried out is not critical.

Wherein a low sulfur fuel is being processed in the present apparatus, it is not necessary to utilize the first contactor-purifier 18 and associated parts and the petrolic liquid leaving flow meter 14 is directed through .valve 16, and valves 15, 25, and 24 being closed, to the second heat exchange unit 26, and on into the second contactorpurifier 27 where sodium compound and vanadium compound removal is carried out.

On the other hand, if the petrolic liquid is low in sodium compounds and vanadium compounds, but the removal of sulfur compounds is necessary, the treated petrolic liquid issuing from the first contactor-purifier 18 is directed through valve 25, valves 24 and 33 being closed, to either the surge tank system or directly through valve 34 to the throttle valve 35.

If the sulfur levels are rather high or the requirements for low sulfur residues in the treated fuel quite stringent, both of the contactor-purifiers 18 and 27 may be set up and supplied with oil-immiscible solvent to carry out sulfur removal in a series or so-called cascade arrangement. If indicated, additional contactor-purifiers may be hooked up in series to carry out even greater purification.

Similarly, both contactor-purifiers, with and without additional contactor-purifiers in series, may be set up and utilized for reducing sodium compounds and vanadium compounds to achieve a lower ash content fuel.

Moreover, it is contemplated that at least one contactor-purified will be used for one of the purification processes while two or more contactor-purifiers in series will be employed for the other purification process in an effort to meet ever rising air pollution and maintenance standards.

EXAMPLES The following examples serve to illustrate the invention and not to limit the scope thereof.

Example 1 Two residual fuel oils, here identified as "Residual Oil A and Residual Oil B, are, at respectively different times, conveyed from on-site storage at an electric generating plant to a model A-1 Podbielniak Contactor operated at a temperature of 120 degrees F. and there contacted with by weight sulfuric acid at a ratio of 0.005 gallon of acid per gallon of oil. The oil feed rate is 0.5 gallon per minute and the rotational speed of the contactor rotor is 7,500 revolutions per minute. The purified oil, in each case, is conveyed to and burned in the burner system of a small steam boiler for a period of 48 hours. The sulfur content of the stack effluent from the burner system does not at any time exceed 10 p.p.m., expressed at H SO In each case, during steady operations, samples are taken of treated and untreated oil and analyzed for sulfur content and physical properties. The results are tabulated as follows:

In further runs according to the invention, the residual oils described in Example 1 are treated with sulfuric acid as described in said example and are then each treated with a 20% by weight aqueous solution of magnesium sulfate in a model A-l Podbielniak Contactor operated at a temperature of about 120 degrees F., to remove so dium and vanadium compounds, the ratio of solution used being about one volume of solution per ten volumes of oil.

The tubes of the boiler used in Example 1 are inspected visually to determine the extent of ash deposits and cleaned, and then used to burn each of the residual oils treated additionally for ash removal for a period of 48 hours, the burners being again inspected and cleaned before and after each run. Visual inspection of ash deposits in each case showed that the amount of deposit laid down in burning each of the oils treated according to this example is about one-tenth of that laid down on burning the oils that are not de-ashed.

In each case, during steady operations, samples are taken of de-ashed oil and oil not de-ashed and analyzed, for sodium and vanadium compound contents. The results are tabulated as follows:

In additional runs according to the invention the method and apparatus of Example 1 are used to desulfurize two different crude oils which are high in sulfur content, but are otherwise suitable to use as fuel. In this case sulfuric acid usage is .01 gallon of 90% by weight sulfuric acid per gallon of crude oil.

Each of the purified oils is burned, respectively, in the burners of a steam generating plant for a period of 48 hours. In each case during steady operations stack effiuent is analyzed and the sulfur content, expressed as H SO is found to be in the range of 15 to p.p.m.

In each case, during steady operations, samples are taken of treated and untreated oil and analyzed for sulfur content and physical properties. The results are tabulated as follows:

Ratawi crude Kuwait crude Untreated Treated Untreated Treated Weight percent sulfur,

expressed as 11280 0.05 Pour point, F 54 Specific gravity... 0. 968

I claim:

conveying the purified petrolic liquid to the burner system,

and burning the purified petrolic liquid substantially without problems caused by deposits of sodium compounds and vanadium compounds on burner components and while maintaining sulfur and sulfur compound concentrations in the stack effluent of the burner system below the maximum permited by air pollution regulations,

said purification system being at least one contactorpurifier and associated oil-immiscible solvent supply and pumps and piping for each problem type of impurity present in the problem petrolic liquid and means for concurrently and sequentially passing the problem petrolic liquid through such at least one type of contactor-purifier for each problem type of impurity present,

and within each contactor-purifier, bringing the problem petrolic liquid into contact with a pre-selected substantially oil-immiscible liquid and maintaining such contact for a sufiicient period of time to reduce the concentration of problem impurity to a level at which the petrolic liquid becomes useful as a fuel with respect to the particular type of impurity, said oil-immiscible liquid being a pro-selected liquid having a substantial solvency for a specific problem impurity present in the problem petrolic liquid.

2. The process as in claim 1 in which the problem types of impurities present in the problem petrolic liquid are (1) sulfur compounds and (2) sodium compounds and vanadium compounds and at least two contactor-purifiers are employed, sulfur compound removal being carried out in at least one contactor-purifier and sodium compound and vanadium compound removal being carried out in at least one contactor-purifier.

3. The process as in claim 1 in which more than one contactor-purifier is used to reduce the concentration of at least one type of impurity and in each such plural use of contactor-purifiers the same are used in series to effect better removal of impurity.

4. The process as in claim 1 in which the problem petrolic liquid contains at least 1 percent by weight of sulfur and sulfur compounds, expressed as H SO and the sulfur content is reduced to below about 0.5 percent by weight.

5. The process as in claim 1 in which the problem petrolic liquid contains sulfur compounds and is treated therefor and the concentration of sulfur and sulfur compounds in the stack effiuent is maintained below about 20 p.p.m., expressed as H SO during regulator operations.

6. The process as in claim 1 in which the problem petrolic liquid contains sulfur compounds and the oil-immiscible liquid used in at least one contactor-purifier is a liquid selected from the group consisting of concentrated sulfuric acid, liquified phenol, liquid sulfur dioxide and sulfolane.

7. The process as in claim l1 in which the problem petrolic liquid contains problem quantities of sodium compounds and vanadium compounds and the oil-immiscible liquid used in at least one contactor-purifier is an aqueous solution of a soluble inorganic compound having a substantial solvency for each of sodium compounds and vanadium compounds present, and the petrolic liquid is contacted with such aqueous solution for a suificient time for the aqueous solution to take up the sodium compounds and vanadium compounds and reduce the residual levels thereof in the petrolic liquid to less than abount 3 p.p.m. of sodium compounds, expressed as Na, and less than about 60 p.p.m. of vanadium compounds, expressed as V.

8. The process as in claim 7 in which the inorganic compound is a water soluble magnesium compound and the aqueous solution contains at least 20 percent by weight thereof.

9. The process as in claim 1 in which the petrolic liquid contains only one of the two types of impurity,

(1) sulfur compounds and (2) sodium compounds and vanadium compounds in problem concentrations and is treated only for that type of impurity.

10. The process as in claim 1 in which at least one of the contactor-purifiers is operated on a substantially continuous basis.

11. The process as in claim 1 in which at least one of the contactor-purifiers is operated on a batch-wise basis and meets the average steady demand of the burner system.

12. The process as in claim 1 in which at least one contactor-purifier is a centrifugal contacting device operated on a substantially continuous basis.

13. The process as in claim 1 in which the petrolic liquid treated in the purification system is conveyed to a surge tank before being fed to the burner system.

14. In combination with a burner system for petrolic liquid and a reservoir for problem petrolic liquid containing at least one type of problem impurity, the combination of parts which comprises:

at least one contactor-purifier for each type of problem impurity for bringing together and then separating immiscible phases,

means for concurrently conveying to each at least one contactor-purifier problem petrolic liquid at a burner system-utilizable rate, from the servoir or other contactor-purifier, and an oil-immiscible liquid capable of taking up a problem impurity from the problem perolic liquid,

within each contactor-purifier, means for bringing a pre-selected oil-immiscible solvent capable of taking up a specific problem impurity, and the petrolic liquid, into contact for a sufficient period of time to permit substantial reduction of the concentration of the specific impurity to a level at which the petrolic liquid is useful as a fuel with respect to such impurity,

10 and separating the oil-immiscible solvent from the petrolic liquid,

and means for conveying the treated petrolic liquid from at least one contactor-purifier to the burner system.

15. The combination as in claim 14 including at least one surge tank connected in series with respect to means for conveying petrolic liquid to the burner.

16. The combination as in claim 14 including means for qauntitatively detecting a phenomenon resulting from burner caloric output, means for feeding a signal from such detector means to a computer pre-programmed to relate such signal to desired flow rate of petrolic liquid to the burner, a control valve in that line which forms part of the means for conveying petrolic liquid to the burner, and means for transmitting a controlling signal from said computer to said control 'valve.

117. The combination as in claim (14 including detector means for quantitatively determining the flow rate of petrolic liquid through the combination; in combination with at least one contactor-purifier, valve means for controlling the ratio of quantity fresh oil-immiscible liquid fed to the contactor to quantity of spent oil-immiscible liquid drawn 01f from the contactor; a ratio controller unit for each said at least one contactor-purifier; and means for transmitting a signal from said detector means to said ratio controller.

References Cited UNITED STATES PATENTS 2,975,594 3/1961 Eastman 43l3 X 3,067,018 12/1962 Voorhees l10l I EDWARD G. FAVORS', Primary Examiner US. Cl. X.R. 43 l-- 

